1. Field of the Invention
The present invention relates to power hand tools, and more particularly to a power hand tool, which allows smooth adjustment of the rotary adjustment knob.
2. Description of the Related Art
A conventional power hand tool with output torque control function, such as a power screwdriver, usually has a circular rotary knob rotatably mounted to the housing thereof for setting the maximum output torque.
In order to set the rotary knob in the adjusted position, the rotary knob has a plurality of positioning grooves on the inner sidewall, and two positioning tongues are set between the rotary knob and the housing of the housing or a component part inside the housing. Each of the two locating tongues has a protruding portion engaged in the positioning grooves of the rotary knob. When turning the rotary knob to adjust the maximum output torque, the user must apply a sufficient force to the rotary knob to overcome the rotary force of the locating tongues.
Because the protruding portions of the locating tongues are selectively engaged into the positioning grooves of the rotary knob in radial direction, it requires many efforts to turn the rotary knob. Further, because the two locating tongues are positioned at two different locations, the installation of the locating tongues is not easy.